Nineteen patients with mycosis fungoides (m.f.), without involvement of lymph nodes and/or internal organs, were treated with oral photochemotherapy (PUVA). After four to five weeks of PUVA therapy (four irradiations/week) complete remission of erythematous and infiltrative plaques occurred; tumorous m.f. lesions also responded to treatment but required longer treatment times. After complete resolution of m.f. lesions the patients were controlled regularly, the observation periods ranging from 6 to 27 months. When recurrences occurred the initial treatment schedule was resumed. Recurrences, more often seen in the tumorous m.f. stage, responded to PUVA equally well as the initial lesions. PUVA therapy of m.f. is thus more effective than conventional UVB-irradiation and less problematic than treatment with cytotoxic agents or ionizing radiation. Present experience indicates that PUVA represents the treatment of choice in early stage m.f.